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Re: [PATCH] xen: fix XEN_DOMCTL_gdbsx_guestmemio crash
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 19 Apr 2022 10:42:32 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Cheyenne Wills <cheyenne.wills@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 19 Apr 2022 08:42:38 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.04.2022 15:31, Juergen Gross wrote:
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -308,7 +308,9 @@ long cf_check
> do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
> if ( op->domain == DOMID_INVALID )
> {
> case XEN_DOMCTL_createdomain:
> +#ifdef CONFIG_GDBSX
> case XEN_DOMCTL_gdbsx_guestmemio:
> +#endif
> d = NULL;
> break;
> }
Wouldn't we be better off simply deleting this case label? dbg_rw_mem()
resolves the domid anyway (exactly as done a few lines down from here),
so I don't see why we couldn't pass a struct domain * there instead of
a domid_t.
This would also reduce the risk of further similar "overrides" appearing
here (taking existing instances as "excuse"), and breaking things again
in a similar way.
And finally I think iommu_do_domctl() needs making resilient against d
coming in as NULL. This isn't just to cover the issue here, but perhaps
more importantly because XEN_DOMCTL_test_assign_device can legitimately
end up having NULL passed here (when the caller passed DOMID_INVALID).
We've simply been lucky that libxl doesn't use this variant of calling
this domctl. I guess when d is NULL we ought to check the global flag
there rather than the per-domain one.
Jan
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